1. Field of the Invention
The present invention relates to an electron emission display device and a control method of the same, and in particular, to an electron emission display device for controlling brightness characteristics in pixels so as to improve uneven light emission between the pixels, and a control method of the same.
2. Discussion of Related Art
An electron emission display device is a flat panel display device that is composed of a cathode, an anode and a gate electrode. More particularly, the cathode usually used as a scanning electrode is formed on a substrate. An insulating layer including an aperture (or a hole) and the gate electrode usually used as a data electrode are laminated on the cathode. In addition, an electron emitter is formed at the interior of the hole of the insulating layer so that it can be connected to the cathode.
The electron emission display device configured thus displays images by centering high electric fields on the emitter to emit electrons using a quantum-mechanical tunnel effect, accelerating the emitted electrons from the emitter using voltage applied between the cathode and the anode to collide with an RGB fluorescent layer formed on the anode, and causing the phosphors of the RGB fluorescent layer to emit light. Brightness of the images, which are displayed by colliding the emitted electrons with the RGB fluorescent layer to cause the phosphors to emit the light, is varied depending on values of the input video data.
FIG. 1 is a diagram showing one example of a configuration of a conventional electron emission display device.
Referring to FIG. 1, the conventional electron emission display device includes a display region 10, a scanning driving unit 20, a data driving unit 30, and a controlling unit 40.
The display region 10 includes a plurality of scanning lines (S1,S2, . . . ,Sn), a plurality of data lines (D1,D2, . . . Dm), and an anode. A plurality of pixels 5 are formed in regions defined by the scanning lines (S1,S2, . . . Sn) and the data lines (D1,D2, . . . Dm) crossing (or intersecting) the scanning lines (S1,S2, . . . Sn). The anode may be formed over the entire display region 10, as shown in FIG. 1. Also, the scanning lines (S1,S2, . . . Sn) are connected with the cathode, and the data lines (D1,D2, . . . Dm) are connected with the gate electrode. Alternatively, the data lines (D1,D2, . . . Dm) are connected with the cathode, and the scanning lines (S1,S2, . . . Sn) are connected with the gate electrode
The scanning driving unit 20 subsequently applies scanning signals to the plurality of scanning lines (S1,S2, . . . Sn).
The data driving unit 30 applies data signals to the plurality of data lines (D1,D2, . . . Dm).
The controlling unit 40 includes a brightness-characteristic detecting unit 41, a compensation coefficient setting unit 42, and a correction unit 43. The brightness-characteristic detecting unit 41 detects brightness characteristics of images displayed by each of the pixels receiving the data signals. The compensation coefficient setting unit 42 stores information detected from the brightness-characteristic detecting unit 41. In addition, the compensation coefficient setting unit 42 resets and stores compensation coefficients by selecting at least one of the pixels 5, and controlling brightness characteristics of the other pixels 5 on the basis of the brightness characteristics of the images displayed by the selected pixel 5. The correction unit 43 compensates the brightness by adding input data corresponding to the brightness desired for the pixels 5 other than the selected pixel to the compensation coefficients stored in the compensation coefficient setting unit 42.
FIG. 2 is a diagram illustrating an addition compensation of the controlling unit 40 employed in the conventional electron emission display device of FIG. 1.
Referring to FIG. 2, the same input data are, for example, applied to each of the pixels 5 of the display region 10 which is shown for simplification purposes to have four pixels 5 so that each of the pixels 5 can display images of the same gray levels. In addition, FIG. 2 shows data lines D1 and D2 and scanning lines S1 and S2. As shown in FIG. 2, maximum brightness level is set to ‘15’, and the input data corresponding to the brightness level of ‘15’ are applied to each of the pixels 5 so that all four pixels 5 can be light-emitted with the brightness level of ‘15’. However, the actual light-emitted brightness may not be at the brightness level of ‘15’, and its difference may be varied depending on each of the pixels 5. The addition compensation process was used in the prior art so as to prevent such uneven brightness of the separate pixels. The addition compensation compensates a brightness level of one or more of the pixels 5 by adding and subtracting the input data applied to each of the pixels. For example, when the input data corresponding to the maximum brightness level ‘15’ is applied to each of the pixels 5, the four pixels 5 actually display the images having brightness levels of ‘15’, ‘14’, ‘13’ and ‘10’, respectively. Accordingly, since the maximum brightness level is ‘15’, no brightness level may be improved more if brightness levels of the other pixels 5 are controlled on the basis of the pixel 5 displaying the brightness of ‘15’. Therefore, when the input data corresponding to ‘15’ is applied, brightness of the other pixels 5 is controlled on the basis of the pixel 5 displaying the brightness level of ‘13’. That is, the brightness is controlled by subtracting the input data of ‘2’ from the pixel 5 displaying the brightness of ‘15’, and subtracting the input data of ‘1’ from the pixel 5 displaying the brightness of ‘14’, but the pixel 5 displaying the brightness of ‘13’ is not controlled since the pixel 5 displaying the brightness of ‘13’ is used as a reference pixel. Also, the brightness may still not be properly controlled (or maintained) because no input data signal is added to the pixel 5 displaying the brightness of ‘10’. After such, an addition driving process needs to be applied to compensate for the uneven brightness level of the images corresponding to most brightness levels of ‘13’.
FIG. 3 is a graph showing brightness characteristics controlled according to a conventional addition compensation process.
Referring to FIG. 3, a brightness curve C1 represents when the addition compensation process is not applied, that is, a brightness curve prior to the compensation; a reference brightness curve C2 represents brightness curves to be compensated; and a brightness curve C3 represents when the addition compensation process is applied, that is, a brightness curve after (or posterior to) the compensation.
As shown in FIG. 3, if an addition compensation process is used as the brightness-curve compensation process of the display region, the brightness level may still not be uniformly compensated even though the compensation coefficients are added and subtracted in brightness sublevels because the compensation coefficients are calculated on the basis of the maximum brightness level.